This invention relates to porous ceramic bodies.
Renewed interest in lightweight porous ceramics has been stimulated by the need for materials having low thermal expansion, low dielectric constant, and/or low density for certain high-tech applications. For example, in space mirror fabrication, there exists a need for a lightweight backing for a 10-meter diameter mirror surface of high optical perfection. The backing, as well as the mirror surface, must have near-zero thermal expansion because of its large size and the need to maintain its optical figure. Another example is in the design of radomes, where a material of low dielectric constant may be required to complete a particular sandwich design. Yet another example is in the manufacture of space shuttle tiles, where good insulation properties have been achieved but dimensional stability on heating during re-entry still poses problems. Ideally, a lightweight porous ceramic body such as an insulating tile, would be formed using a bonding agent, such as silica, with fibers having low thermal expansion, such as silica fibers. Unfortunately, the high temperatures required for such a process as well as the chemical reactions that might occur between the materials at high temperatures have made such forming methods impractical. Further, addition of fluxing agents to reduce the required processing temperatures have led to increased thermal expansion of the bonding agent, thereby decreasing the operational temperature of the tile.
Accordingly, it is an object of the present invention to provide an improved method for fabricating porous ceramic bodies.
it is another object of the present invention to provide a porous ceramic body.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art after review of the following detailed description of the invention.